ZSW raises thin-film PV efficiency record from 21% to 21.7%

Using a solar cell made of copper indium gallium diselenide (CIGS), ZSW (Zentrum für Sonnenenergie- und Wasserstoff-Forschung — or Center for Solar Energy and Hydrogen Research — Baden-Württemberg) of Stuttgart, Germany has regained the thin-film photovoltaic efficiency record, raising it from 21% (set by researchers in Sweden in June) to 21.7%, as confirmed by Fraunhofer Institute for Solar Energy Systems ISE. ZSW had previously raised the record from 20.3% (set in August 2010) to 20.8% (set in November 2013).

The record extends the CIGS PV cell’s lead in solar energy conversion efficiency over multicrystalline solar cells (which still dominate the market) to 1.3%. “Our advances once again confirm the tremendous technological potential of CIGS thin-film photovoltaics,” says professor Michael Powalla, ZSW board member and head of its Photovoltaics division. “The lab data show that further efficiency improvements will be possible in the years ahead. This could drive down the cost of CIGS technology even more sharply,” he adds.

Picture:
A cell strip with the record-setting solar cell (left) and a ZSW researcher with several cell strips (right).

Covering an area of 0.5cm2 (a standard size for such tests), the record cell was manufactured in a laboratory coating system using the co-evaporation process, which is highly reproducible in the lab( more than 40 cells were made with efficiency ratings exceeding 21%), indicating that the method lends itself to industrial manufacturing and could readily be scaled up to mass production.

“It will probably take some time for this efficiency increase to make its way into module manufacturing, but 17-19% is very much possible in the next few years,” reckons Powalla. CIGS modules currently on the market are rated at about 15% efficiency. However, the physical area of modules is larger, so they are less efficient than solar cells.

ZSW reckons that its latest results improve the chances of CIGS thin-film technology gaining a large share of the market. This is good news for Reutlingen-based Manz AG. ZSW licensed the technology to Manz and developed it jointly with this industry partner. The firm exclusively markets a turnkey manufacturing line for producing CIGS thin-film solar panels and now aims to transition this increase in efficiency out of the lab and into the factory. The aim is to make CIGS solar systems economical and affordable practically anywhere in the world.

The coating of thin-film cells is measured in microns, so they consume far less material and energy in their manufacturing than standard solar cells and can hence have a major impact on cutting future production costs, says ZSW. This is why the Germany Federal Ministries for the Environment and for Economic Affairs and Energy as well as the state of Baden-Württemberg have provided funding for the technology. “The roughly 4m euros in basic funding flowing to the ZSW every year from the state is money well spent,” comments Baden-Württemberg's Minister of Finance and Economics Dr Nils Schmid.

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